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	$179.49	3.224%	$185.2768	$185.28	$185.30	$185.30
Purchase #2	$159.52	9.289%	$174.3378	$174.34	$174.35	$174.30
Purchase #3	$99.29	11.238%	$110.4482	$110.45	$110.45	$110.40
Purchase #4	$171.90	10.105%	$189.2705	$189.27	$189.25	$189.30
Purchase #5	$96.48	7.427%	$103.6456	$103.65	$103.65	$103.60
Purchase #6	$183.54	4.139%	$191.1367	$191.14	$191.15	$191.10
Purchase #7	$63.77	5.373%	$67.1964	$67.20	$67.20	$67.20
7 purchase totals =	$953.99		$1,021.3120	$1,021.33	$1,021.35	$1,021.20