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	$119.80	6.518%	$127.6086	$127.61	$127.60	$127.60
Purchase #2	$227.79	4.112%	$237.1567	$237.16	$237.15	$237.20
Purchase #3	$150.84	13.570%	$171.309	$171.31	$171.30	$171.30
Purchase #4	$123.69	8.229%	$133.8685	$133.87	$133.85	$133.90
Purchase #5	$91.91	5.413%	$96.8851	$96.89	$96.90	$96.90
Purchase #6	$14.89	3.471%	$15.4068	$15.41	$15.40	$15.40
Purchase #7	$5.72	6.563%	$6.0954	$6.10	$6.10	$6.10
7 purchase totals =	$734.64		$788.3301	$788.35	$788.30	$788.40