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	$96.87	13.538%	$109.9843	$109.98	$110.00	$110.00
Purchase #2	$230.53	6.636%	$245.828	$245.83	$245.85	$245.80
Purchase #3	$101.82	7.366%	$109.3201	$109.32	$109.30	$109.30
Purchase #4	$42.81	3.484%	$44.3015	$44.30	$44.30	$44.30
Purchase #5	$145.81	9.253%	$159.3018	$159.30	$159.30	$159.30
Purchase #6	$92.62	13.531%	$105.1524	$105.15	$105.15	$105.20
Purchase #7	$69.46	11.609%	$77.5236	$77.52	$77.50	$77.50
7 purchase totals =	$779.92		$851.4117	$851.40	$851.40	$851.40