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	$215.67	7.394%	$231.6166	$231.62	$231.60	$231.60
Purchase #2	$110.33	4.680%	$115.4934	$115.49	$115.50	$115.50
Purchase #3	$222.71	11.317%	$247.9141	$247.91	$247.90	$247.90
Purchase #4	$99.60	12.641%	$112.1904	$112.19	$112.20	$112.20
Purchase #5	$86.84	11.188%	$96.5557	$96.56	$96.55	$96.60
Purchase #6	$150.88	3.571%	$156.2679	$156.27	$156.25	$156.30
Purchase #7	$67.57	6.756%	$72.135	$72.14	$72.15	$72.10
7 purchase totals =	$953.60		$1,032.1731	$1,032.18	$1,032.15	$1,032.20