Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$194.31	12.782%	$219.1467	$219.15	$219.15	$219.10
Purchase #2	$170.91	12.133%	$191.6465	$191.65	$191.65	$191.60
Purchase #3	$162.90	10.288%	$179.6592	$179.66	$179.65	$179.70
Purchase #4	$213.82	10.262%	$235.7622	$235.76	$235.75	$235.80
Purchase #5	$10.57	12.475%	$11.8886	$11.89	$11.90	$11.90
Purchase #6	$132.32	11.702%	$147.8041	$147.80	$147.80	$147.80
Purchase #7	$196.86	6.798%	$210.2425	$210.24	$210.25	$210.20
7 purchase totals =	$1,081.69		$1,196.1498	$1,196.15	$1,196.15	$1,196.10