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	$140.69	7.702%	$151.5259	$151.53	$151.55	$151.50
Purchase #2	$76.82	8.410%	$83.2806	$83.28	$83.30	$83.30
Purchase #3	$196.96	7.157%	$211.0564	$211.06	$211.05	$211.10
Purchase #4	$247.47	6.687%	$264.0183	$264.02	$264.00	$264.00
Purchase #5	$22.68	13.585%	$25.7611	$25.76	$25.75	$25.80
Purchase #6	$223.75	9.710%	$245.4761	$245.48	$245.50	$245.50
Purchase #7	$115.85	3.451%	$119.848	$119.85	$119.85	$119.80
7 purchase totals =	$1,024.22		$1,100.9664	$1,100.98	$1,101.00	$1,101.00