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	$165.29	5.607%	$174.5578	$174.56	$174.55	$174.60
Purchase #2	$239.67	4.425%	$250.2754	$250.28	$250.30	$250.30
Purchase #3	$110.92	12.753%	$125.0656	$125.07	$125.05	$125.10
Purchase #4	$224.25	8.547%	$243.4166	$243.42	$243.40	$243.40
Purchase #5	$121.88	4.207%	$127.0075	$127.01	$127.00	$127.00
Purchase #6	$28.90	13.756%	$32.8755	$32.88	$32.90	$32.90
Purchase #7	$111.98	13.534%	$127.1354	$127.14	$127.15	$127.10
7 purchase totals =	$1,002.89		$1,080.3338	$1,080.36	$1,080.35	$1,080.40