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	$232.54	6.317%	$247.2296	$247.23	$247.25	$247.20
Purchase #2	$174.56	3.166%	$180.0866	$180.09	$180.10	$180.10
Purchase #3	$104.28	3.673%	$108.1102	$108.11	$108.10	$108.10
Purchase #4	$87.44	13.656%	$99.3808	$99.38	$99.40	$99.40
Purchase #5	$119.85	6.159%	$127.2316	$127.23	$127.25	$127.20
Purchase #6	$98.25	4.866%	$103.0308	$103.03	$103.05	$103.00
Purchase #7	$207.61	4.361%	$216.6639	$216.66	$216.65	$216.70
7 purchase totals =	$1,024.53		$1,081.7335	$1,081.73	$1,081.80	$1,081.70