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	$43.96	7.671%	$47.3322	$47.33	$47.35	$47.30
Purchase #2	$64.46	13.111%	$72.9114	$72.91	$72.90	$72.90
Purchase #3	$149.64	12.466%	$168.2941	$168.29	$168.30	$168.30
Purchase #4	$74.96	5.319%	$78.9471	$78.95	$78.95	$78.90
Purchase #5	$25.34	12.206%	$28.433	$28.43	$28.45	$28.40
Purchase #6	$43.75	8.718%	$47.5641	$47.56	$47.55	$47.60
Purchase #7	$90.92	10.415%	$100.3893	$100.39	$100.40	$100.40
7 purchase totals =	$493.03		$543.8712	$543.86	$543.90	$543.80