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	$24.82	3.673%	$25.7316	$25.73	$25.75	$25.70
Purchase #2	$162.52	13.732%	$184.8372	$184.84	$184.85	$184.80
Purchase #3	$54.97	7.676%	$59.1895	$59.19	$59.20	$59.20
Purchase #4	$105.62	12.468%	$118.7887	$118.79	$118.80	$118.80
Purchase #5	$62.61	13.221%	$70.8877	$70.89	$70.90	$70.90
Purchase #6	$232.76	13.851%	$264.9996	$265.00	$265.00	$265.00
Purchase #7	$41.30	3.596%	$42.7851	$42.79	$42.80	$42.80
7 purchase totals =	$684.60		$767.2194	$767.23	$767.30	$767.20