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	$64.76	12.555%	$72.8906	$72.89	$72.90	$72.90
Purchase #2	$190.73	4.261%	$198.857	$198.86	$198.85	$198.90
Purchase #3	$216.30	7.374%	$232.25	$232.25	$232.25	$232.30
Purchase #4	$250.96	13.618%	$285.1357	$285.14	$285.15	$285.10
Purchase #5	$165.55	5.284%	$174.2977	$174.30	$174.30	$174.30
Purchase #6	$163.50	4.766%	$171.2924	$171.29	$171.30	$171.30
Purchase #7	$145.33	5.535%	$153.374	$153.37	$153.35	$153.40
7 purchase totals =	$1,197.13		$1,288.0974	$1,288.10	$1,288.10	$1,288.20