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	$174.88	6.867%	$186.889	$186.89	$186.90	$186.90
Purchase #2	$105.85	7.224%	$113.4966	$113.50	$113.50	$113.50
Purchase #3	$61.74	4.374%	$64.4405	$64.44	$64.45	$64.40
Purchase #4	$28.28	12.673%	$31.8639	$31.86	$31.85	$31.90
Purchase #5	$184.49	3.613%	$191.1556	$191.16	$191.15	$191.20
Purchase #6	$99.52	4.777%	$104.2741	$104.27	$104.25	$104.30
Purchase #7	$210.40	10.480%	$232.4499	$232.45	$232.45	$232.40
7 purchase totals =	$865.16		$924.5696	$924.57	$924.55	$924.60