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	$33.84	10.336%	$37.3377	$37.34	$37.35	$37.30
Purchase #2	$163.46	5.396%	$172.2803	$172.28	$172.30	$172.30
Purchase #3	$104.91	4.524%	$109.6561	$109.66	$109.65	$109.70
Purchase #4	$137.86	6.848%	$147.3007	$147.30	$147.30	$147.30
Purchase #5	$90.62	9.701%	$99.411	$99.41	$99.40	$99.40
Purchase #6	$69.62	12.199%	$78.1129	$78.11	$78.10	$78.10
Purchase #7	$96.41	5.486%	$101.6991	$101.70	$101.70	$101.70
7 purchase totals =	$696.72		$745.7978	$745.80	$745.80	$745.80