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	$181.98	6.299%	$193.4429	$193.44	$193.45	$193.40
Purchase #2	$57.56	3.529%	$59.5913	$59.59	$59.60	$59.60
Purchase #3	$152.51	6.252%	$162.0449	$162.04	$162.05	$162.00
Purchase #4	$187.50	8.491%	$203.4206	$203.42	$203.40	$203.40
Purchase #5	$78.50	4.532%	$82.0576	$82.06	$82.05	$82.10
Purchase #6	$34.60	7.658%	$37.2497	$37.25	$37.25	$37.20
Purchase #7	$234.41	13.349%	$265.7014	$265.70	$265.70	$265.70
7 purchase totals =	$927.06		$1,003.5084	$1,003.50	$1,003.50	$1,003.40