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	$182.99	4.443%	$191.1202	$191.12	$191.10	$191.10
Purchase #2	$204.74	7.227%	$219.5366	$219.54	$219.55	$219.50
Purchase #3	$137.42	13.651%	$156.1792	$156.18	$156.20	$156.20
Purchase #4	$31.67	12.585%	$35.6557	$35.66	$35.65	$35.70
Purchase #5	$187.94	4.527%	$196.448	$196.45	$196.45	$196.40
Purchase #6	$199.62	6.251%	$212.0982	$212.10	$212.10	$212.10
Purchase #7	$77.69	11.805%	$86.8613	$86.86	$86.85	$86.90
7 purchase totals =	$1,022.07		$1,097.8992	$1,097.91	$1,097.90	$1,097.90