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	$122.51	3.759%	$127.1152	$127.12	$127.10	$127.10
Purchase #2	$242.28	9.286%	$264.7781	$264.78	$264.80	$264.80
Purchase #3	$69.55	3.742%	$72.1526	$72.15	$72.15	$72.20
Purchase #4	$164.25	6.693%	$175.2433	$175.24	$175.25	$175.20
Purchase #5	$206.94	5.870%	$219.0874	$219.09	$219.10	$219.10
Purchase #6	$86.39	5.683%	$91.2995	$91.30	$91.30	$91.30
Purchase #7	$166.39	11.367%	$185.3036	$185.30	$185.30	$185.30
7 purchase totals =	$1,058.31		$1,134.9797	$1,134.98	$1,135.00	$1,135.00