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	$137.53	13.842%	$156.5669	$156.57	$156.55	$156.60
Purchase #2	$148.98	13.556%	$169.1757	$169.18	$169.20	$169.20
Purchase #3	$217.69	6.303%	$231.411	$231.41	$231.40	$231.40
Purchase #4	$91.31	8.829%	$99.3718	$99.37	$99.35	$99.40
Purchase #5	$59.64	4.616%	$62.393	$62.39	$62.40	$62.40
Purchase #6	$131.44	8.196%	$142.2128	$142.21	$142.20	$142.20
Purchase #7	$223.92	7.586%	$240.9066	$240.91	$240.90	$240.90
7 purchase totals =	$1,010.51		$1,102.0378	$1,102.04	$1,102.00	$1,102.10