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	$186.89	4.615%	$195.515	$195.52	$195.50	$195.50
Purchase #2	$80.76	11.182%	$89.7906	$89.79	$89.80	$89.80
Purchase #3	$148.86	10.576%	$164.6034	$164.60	$164.60	$164.60
Purchase #4	$108.31	11.673%	$120.953	$120.95	$120.95	$121.00
Purchase #5	$105.74	3.469%	$109.4081	$109.41	$109.40	$109.40
Purchase #6	$115.63	8.478%	$125.4331	$125.43	$125.45	$125.40
Purchase #7	$247.76	12.152%	$277.8678	$277.87	$277.85	$277.90
7 purchase totals =	$993.95		$1,083.5710	$1,083.57	$1,083.55	$1,083.60