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	$35.96	3.785%	$37.3211	$37.32	$37.30	$37.30
Purchase #2	$110.61	3.347%	$114.3121	$114.31	$114.30	$114.30
Purchase #3	$166.42	11.857%	$186.1524	$186.15	$186.15	$186.20
Purchase #4	$147.46	6.207%	$156.6128	$156.61	$156.60	$156.60
Purchase #5	$145.56	11.667%	$162.5425	$162.54	$162.55	$162.50
Purchase #6	$168.58	11.687%	$188.2819	$188.28	$188.30	$188.30
Purchase #7	$141.65	13.542%	$160.8322	$160.83	$160.85	$160.80
7 purchase totals =	$916.24		$1,006.0550	$1,006.04	$1,006.05	$1,006.00