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	$125.68	11.307%	$139.8906	$139.89	$139.90	$139.90
Purchase #2	$18.51	3.542%	$19.1656	$19.17	$19.15	$19.20
Purchase #3	$61.61	10.592%	$68.1357	$68.14	$68.15	$68.10
Purchase #4	$196.28	4.826%	$205.7525	$205.75	$205.75	$205.80
Purchase #5	$89.78	10.380%	$99.0992	$99.10	$99.10	$99.10
Purchase #6	$147.75	8.399%	$160.1595	$160.16	$160.15	$160.20
Purchase #7	$145.61	5.160%	$153.1235	$153.12	$153.10	$153.10
7 purchase totals =	$785.22		$845.3266	$845.33	$845.30	$845.40