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	$92.32	12.496%	$103.8563	$103.86	$103.85	$103.90
Purchase #2	$243.44	4.124%	$253.4795	$253.48	$253.50	$253.50
Purchase #3	$247.52	8.466%	$268.475	$268.48	$268.50	$268.50
Purchase #4	$165.60	11.872%	$185.26	$185.26	$185.25	$185.30
Purchase #5	$226.56	4.773%	$237.3737	$237.37	$237.35	$237.40
Purchase #6	$53.61	13.168%	$60.6694	$60.67	$60.65	$60.70
Purchase #7	$79.50	3.542%	$82.3159	$82.32	$82.30	$82.30
7 purchase totals =	$1,108.55		$1,191.4298	$1,191.44	$1,191.40	$1,191.60