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	$177.54	7.815%	$191.4148	$191.41	$191.40	$191.40
Purchase #2	$130.90	12.535%	$147.3083	$147.31	$147.30	$147.30
Purchase #3	$35.25	11.506%	$39.3059	$39.31	$39.30	$39.30
Purchase #4	$231.93	11.802%	$259.3024	$259.30	$259.30	$259.30
Purchase #5	$45.57	10.189%	$50.2131	$50.21	$50.20	$50.20
Purchase #6	$196.90	9.390%	$215.3889	$215.39	$215.40	$215.40
Purchase #7	$135.56	10.777%	$150.1693	$150.17	$150.15	$150.20
7 purchase totals =	$953.65		$1,053.1027	$1,053.10	$1,053.05	$1,053.10