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	$145.60	3.327%	$150.4441	$150.44	$150.45	$150.40
Purchase #2	$98.95	7.137%	$106.0121	$106.01	$106.00	$106.00
Purchase #3	$115.32	10.317%	$127.2176	$127.22	$127.20	$127.20
Purchase #4	$43.60	5.280%	$45.9021	$45.90	$45.90	$45.90
Purchase #5	$185.63	10.619%	$205.342	$205.34	$205.35	$205.30
Purchase #6	$249.79	5.401%	$263.2812	$263.28	$263.30	$263.30
Purchase #7	$100.41	5.232%	$105.6635	$105.66	$105.65	$105.70
7 purchase totals =	$939.30		$1,003.8626	$1,003.85	$1,003.85	$1,003.80