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	$129.83	9.711%	$142.4378	$142.44	$142.45	$142.40
Purchase #2	$245.94	3.641%	$254.8947	$254.89	$254.90	$254.90
Purchase #3	$78.62	9.647%	$86.2045	$86.20	$86.20	$86.20
Purchase #4	$129.75	10.609%	$143.5152	$143.52	$143.50	$143.50
Purchase #5	$223.57	9.254%	$244.2592	$244.26	$244.25	$244.30
Purchase #6	$114.37	5.419%	$120.5677	$120.57	$120.55	$120.60
Purchase #7	$9.71	5.404%	$10.2347	$10.23	$10.25	$10.20
7 purchase totals =	$931.79		$1,002.1138	$1,002.11	$1,002.10	$1,002.10