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	$181.28	9.299%	$198.1372	$198.14	$198.15	$198.10
Purchase #2	$119.56	3.782%	$124.0818	$124.08	$124.10	$124.10
Purchase #3	$219.63	4.431%	$229.3618	$229.36	$229.35	$229.40
Purchase #4	$31.58	11.647%	$35.2581	$35.26	$35.25	$35.30
Purchase #5	$244.48	9.252%	$267.0993	$267.10	$267.10	$267.10
Purchase #6	$119.57	6.544%	$127.3947	$127.39	$127.40	$127.40
Purchase #7	$94.36	6.107%	$100.1226	$100.12	$100.10	$100.10
7 purchase totals =	$1,010.46		$1,081.4555	$1,081.45	$1,081.45	$1,081.50