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	$173.36	12.798%	$195.5466	$195.55	$195.55	$195.50
Purchase #2	$127.48	9.578%	$139.69	$139.69	$139.70	$139.70
Purchase #3	$79.31	13.213%	$89.7892	$89.79	$89.80	$89.80
Purchase #4	$198.87	3.680%	$206.1884	$206.19	$206.20	$206.20
Purchase #5	$35.56	8.393%	$38.5446	$38.54	$38.55	$38.50
Purchase #6	$56.95	11.707%	$63.6171	$63.62	$63.60	$63.60
Purchase #7	$250.77	7.162%	$268.7301	$268.73	$268.75	$268.70
7 purchase totals =	$922.30		$1,002.1060	$1,002.11	$1,002.15	$1,002.00