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	$178.39	5.812%	$188.758	$188.76	$188.75	$188.80
Purchase #2	$123.90	5.774%	$131.054	$131.05	$131.05	$131.10
Purchase #3	$79.41	7.331%	$85.2315	$85.23	$85.25	$85.20
Purchase #4	$92.65	12.526%	$104.2553	$104.26	$104.25	$104.30
Purchase #5	$102.57	6.403%	$109.1376	$109.14	$109.15	$109.10
Purchase #6	$93.78	12.136%	$105.1611	$105.16	$105.15	$105.20
Purchase #7	$40.81	7.362%	$43.8144	$43.81	$43.80	$43.80
7 purchase totals =	$711.51		$767.4119	$767.41	$767.40	$767.50