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	$221.77	9.793%	$243.4879	$243.49	$243.50	$243.50
Purchase #2	$110.86	13.675%	$126.0201	$126.02	$126.00	$126.00
Purchase #3	$226.30	8.400%	$245.3092	$245.31	$245.30	$245.30
Purchase #4	$116.29	8.668%	$126.37	$126.37	$126.35	$126.40
Purchase #5	$80.77	12.827%	$91.1304	$91.13	$91.15	$91.10
Purchase #6	$137.75	13.356%	$156.1479	$156.15	$156.15	$156.10
Purchase #7	$134.58	13.442%	$152.6702	$152.67	$152.65	$152.70
7 purchase totals =	$1,028.32		$1,141.1357	$1,141.14	$1,141.10	$1,141.10