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	$160.46	4.182%	$167.1704	$167.17	$167.15	$167.20
Purchase #2	$181.51	8.462%	$196.8694	$196.87	$196.85	$196.90
Purchase #3	$59.73	3.850%	$62.0296	$62.03	$62.05	$62.00
Purchase #4	$245.69	5.163%	$258.375	$258.38	$258.40	$258.40
Purchase #5	$82.59	10.548%	$91.3016	$91.30	$91.30	$91.30
Purchase #6	$60.72	6.694%	$64.7846	$64.78	$64.80	$64.80
Purchase #7	$105.63	3.276%	$109.0904	$109.09	$109.10	$109.10
7 purchase totals =	$896.33		$949.6210	$949.62	$949.65	$949.70