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	$155.89	5.720%	$164.8069	$164.81	$164.80	$164.80
Purchase #2	$83.37	7.681%	$89.7736	$89.77	$89.75	$89.80
Purchase #3	$58.26	11.443%	$64.9267	$64.93	$64.95	$64.90
Purchase #4	$155.43	4.813%	$162.9108	$162.91	$162.90	$162.90
Purchase #5	$167.58	5.486%	$176.7734	$176.77	$176.75	$176.80
Purchase #6	$76.74	12.458%	$86.3003	$86.30	$86.30	$86.30
Purchase #7	$55.27	9.807%	$60.6903	$60.69	$60.70	$60.70
7 purchase totals =	$752.54		$806.1820	$806.18	$806.15	$806.20