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	$158.61	3.729%	$164.5246	$164.52	$164.50	$164.50
Purchase #2	$86.64	11.445%	$96.5559	$96.56	$96.55	$96.60
Purchase #3	$165.78	7.548%	$178.2931	$178.29	$178.30	$178.30
Purchase #4	$198.95	7.322%	$213.5171	$213.52	$213.50	$213.50
Purchase #5	$174.34	10.297%	$192.2918	$192.29	$192.30	$192.30
Purchase #6	$163.50	13.465%	$185.5153	$185.52	$185.50	$185.50
Purchase #7	$27.32	10.245%	$30.1189	$30.12	$30.10	$30.10
7 purchase totals =	$975.14		$1,060.8167	$1,060.82	$1,060.75	$1,060.80