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	$220.80	10.850%	$244.7568	$244.76	$244.75	$244.80
Purchase #2	$98.88	11.139%	$109.8942	$109.89	$109.90	$109.90
Purchase #3	$175.31	5.503%	$184.9573	$184.96	$184.95	$185.00
Purchase #4	$195.86	7.453%	$210.4574	$210.46	$210.45	$210.50
Purchase #5	$106.50	5.119%	$111.9517	$111.95	$111.95	$112.00
Purchase #6	$244.76	9.303%	$267.53	$267.53	$267.55	$267.50
Purchase #7	$53.45	5.805%	$56.5528	$56.55	$56.55	$56.60
7 purchase totals =	$1,095.56		$1,186.1002	$1,186.10	$1,186.10	$1,186.30