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	$100.69	4.230%	$104.9492	$104.95	$104.95	$104.90
Purchase #2	$135.46	5.377%	$142.7437	$142.74	$142.75	$142.70
Purchase #3	$67.31	6.112%	$71.424	$71.42	$71.40	$71.40
Purchase #4	$25.48	11.306%	$28.3608	$28.36	$28.35	$28.40
Purchase #5	$89.56	12.623%	$100.8652	$100.87	$100.85	$100.90
Purchase #6	$121.87	4.361%	$127.1848	$127.18	$127.20	$127.20
Purchase #7	$142.48	9.588%	$156.141	$156.14	$156.15	$156.10
7 purchase totals =	$682.85		$731.6687	$731.66	$731.65	$731.60