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	$165.65	4.702%	$173.4389	$173.44	$173.45	$173.40
Purchase #2	$152.45	8.598%	$165.5577	$165.56	$165.55	$165.60
Purchase #3	$78.54	13.808%	$89.3848	$89.38	$89.40	$89.40
Purchase #4	$91.70	9.352%	$100.2758	$100.28	$100.30	$100.30
Purchase #5	$248.84	5.405%	$262.2898	$262.29	$262.30	$262.30
Purchase #6	$129.80	6.179%	$137.8203	$137.82	$137.80	$137.80
Purchase #7	$193.46	8.165%	$209.256	$209.26	$209.25	$209.30
7 purchase totals =	$1,060.44		$1,138.0233	$1,138.03	$1,138.05	$1,138.10