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	$141.94	5.435%	$149.6544	$149.65	$149.65	$149.70
Purchase #2	$118.32	9.818%	$129.9367	$129.94	$129.95	$129.90
Purchase #3	$171.46	5.631%	$181.1149	$181.11	$181.10	$181.10
Purchase #4	$179.98	3.298%	$185.9157	$185.92	$185.90	$185.90
Purchase #5	$79.51	4.220%	$82.8653	$82.87	$82.85	$82.90
Purchase #6	$237.34	5.490%	$250.37	$250.37	$250.35	$250.40
Purchase #7	$84.47	5.589%	$89.191	$89.19	$89.20	$89.20
7 purchase totals =	$1,013.02		$1,069.0480	$1,069.05	$1,069.00	$1,069.10