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	$184.56	8.862%	$200.9157	$200.92	$200.90	$200.90
Purchase #2	$21.33	12.774%	$24.0547	$24.05	$24.05	$24.10
Purchase #3	$55.48	6.458%	$59.0629	$59.06	$59.05	$59.10
Purchase #4	$219.73	4.399%	$229.3959	$229.40	$229.40	$229.40
Purchase #5	$152.28	8.730%	$165.574	$165.57	$165.55	$165.60
Purchase #6	$246.96	9.497%	$270.4138	$270.41	$270.40	$270.40
Purchase #7	$43.72	4.861%	$45.8452	$45.85	$45.85	$45.80
7 purchase totals =	$924.06		$995.2622	$995.26	$995.20	$995.30